Fuel starvation?

[seanycozzie16v]

So was on the dual carriageway nicely tootling along at 60 when the bike just lost all power and died. This was at full throttle. Let the throttle off and started pumping it to get it to go again. It eventually did and power came back but it was spluttering and everything. It's as if it was being starved of fuel. Did it again at a junction. Started back up again but was very hesitant at revving at idle. Like a delay. Pulled the plugs out. They are new btw and they are like a browny white with no blackness to then at all?

[seanycozzie16v]

Round town though it runs quite nicely. Not running full throttle though. Has a very rough idle also. Sometimes it will idle but most of the time the revs drop very slowly and it just cuts out

[eastanglianbiker]

you need to find out if you have got a fuel starvation problem ride the bike and as it cuts out and stops open the fuel cap listen for it hissing or the sound of air rushing in it could be a blocked breather hole in the fuel cap

[seanycozzie16v]

Tried that no hissing or.anything

[Tango]

Does sound like a blocked tank breather to me too........and the idle mixture screw sounds like it could do with a tweak......

[seanycozzie16v]

Screwing out the mixture screw makes it richer correct?

[eastanglianbiker]

check how many turns the mixture screw is out by counting it as you screw it in then bring it back out about 1 1/2 to 1 3/4 turns and see how it is

[fredc]

check how many turns the mixture screw is out by counting it as you screw it in then bring it back out about 1 1/2 to 1 3/4 turns and see how it is

 

don't screw it in tight, you'll damage the tip

[seanycozzie16v]

found the issue. pulled the float bowl off and found a bit of dirt lying at the bottom of the bowl. adjusted the float height again and also added a inline filter to catch any dirt from the tank. seems to be ok now. but i find i have to run a tiny bit of choke all the time to keep it running

[eastanglianbiker]

then it isnt right it must be running to lean (not enough fuel )

[seanycozzie16v]

mixture screw? tried that makes no difference to the running. usually you would hear the revs rise when screwing it out? i get nothing

[Mr Fro]

Have you cleaned it? Get some spray carb cleaner (£6-7 from Halfords), take all the jets, screws, tubes, floats etc out of the carb and spray it in all the knooks and crannies and through any holes and such.

[seanycozzie16v]

been taken apart and cleaned numerous times. i've been thinking. i fancy upping the size of the jets to the next size. main jet and pilot jet. they are only a couple of quid on ebay so should i? the pilot jet in this mikuni bds26 carb is a #20 and the main jet is a 102.5. i'm really at my wits end here

[Mr Fro]

Are they the correct sizes in there at the mo? I'd be tempted to get a fresh set of jets and screws in case the old ones are damaged (easily done) and sonicate the carb body. Changing the jet sizes only works if you know everything else is functioning correctly. From what you've said, it sounds like you still have a blockage.